LyX can't find most document classes.

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https://bbs.archlinux.org – I just tried to re-open an old LyX document that I put together a while back. On opening, I have this error:The selected document class article requires external files that are not available. The document class can still be used, but the document cannot be compiled until the following prerequisites are installed: article.cls See section (Class Availability) of the User's Guide for more information.If I go to Document > Setting > Document class. 90% of the classes are unavailable, except a few called DocBook and one called AGU article. I'm not sure why any files have g (HowTos)